http://techreport.com/discussions.x/16686
I have built 2 Asus machines this month and in both cases, if I set thwe BIOS to control the fan speeds, it'll chuck a wobbler when I boot them up after a cold start because the fan's "not working" even though it just spooled up and slowed.
My intel mobo has 2 headers that do a great job.. and one that just revs it up and down like a Chav at the lights in his Saxo...
I'm not alone!